Such a device is already known and is used, among other things, for testing the elongation properties of rubber under this state of tension.
This known device is provided with two pulling elements arranged perpendicular to one another. A rubber test specimen is capable of being placed in the plane of the stress to be produced. Two adjacent sides of the plate are connected with the pulling elements, the tensile force thereof being perpendicular to the associated side. The two other sides are fixed, in the direction of the force exerted on the opposing side, by a stationary part of the device.
This known device is very complex and therefore costly. In addition, the two pulling elements must exhibit a very good synchronous action together in order to obtain accurate and reproducible test results.
The object of the invention is to procure a device of the sort mentioned at the beginning wherein the drawbacks described above are effectively eliminated.
To this end, the device according to the invention is characterized in that one drawplate is provided, while force transmitters distribute a uniaxial force exerted on the drawplate via rerouting elements over the clamps.
The means accordingly need not have any specially designed pulling elements, but may be placed in a standard draw bench, which makes the entire test setup simpler and cheaper.
In addition, there are no longer any problems of synchronization, because only a single force is exerted.
Further, it is no longer necessary to use a square test specimen, as the direction of the tensile force at the clamps, owing to the rerouting elements, is independent of the direction of the tensile force at the drawplate.
In a favorable embodiment of the device according to the invention the clamps are mounted with a regular distribution, being radially displaceable, and the clamps are preferably placed in a circular arrangement. In this way a circular rubber disk may be utilized as test specimen. This has the advantage that a purely radial state of tension is produced, where the force transmitted by the clamps to the body lies in line with the displacement of the clamp caused by the deformation of the body.
The lateral displacement of the clamp necessary when a square test specimen is stressed, which is produced owing to the fact that the direction of the deformation and the force do not coincide, does not occur in this embodiment.
Owing to this the special provisions which make such lateral displacement possible are omitted, so that the device may be even more simply designed.
An advantageously applicable embodiment of the device according to the invention is characterized in that the uniaxial force exerted on the drawplate is at least approximately perpendicular to the plane of the body to be stressed.
In this way a rotationally symmetric arrangement may be obtained, which has a positive influence on the accuracy of the state of tension produced.
In an advantageously applied embodiment of the device according to the invention the force transmitters consist of cables, while the rerouting elements are designed as rerouting wheels which reroute the cables from the drawplate to the clamps.